One of the weirder problems in fusion engineering is that everything I design has to take transmutation into account. It’s a bit of a pain in the neck, particularly when I’m accidentally turning silver into cadmium.
Transmutation was first observed in the early 20th century, when Frederick Soddy and Ernest Rutherford realized that their radium was turning itself into thorium. Soddy was the first one to use the word, to which Rutherford replied, “for Christ's sake, Soddy, don't call it transmutation. They'll have our heads off as alchemists!”
These days, one of the easier ways to induce transmutation in otherwise stable elements is to bombard them with neutron radiation. When a fusion reactor is burning a deuterium-tritium fuel mixture, there are just. So many neutrons. I’ve designed stuff for a tokamak that was running on just deuterium, and that was way more forgiving. By comparison to a D-T tokamak like SPARC, the neutron flux was basically a warm summer breeze.
So, not only does everything have to take the massive heat loads, magnetic fields, and electrical forces of a tokamak, I have to make sure it doesn’t transmute into anything stupid in the process. I don’t have the luxury of being able to use water shielding, either. I’m putting stuff, like, centimeters away from the fusion plasma, with nothing in between but vacuum and wishes.
Fortunately for me, this isn’t as big a problem as you might expect. Some elements are way harder to transmute than others. Like, nickel will start turning into iron and cobalt pretty fast, but you can blast beryllium with neutrons until the cows come home. Right now, my biggest headache is silver.
A lot of my designs need to be brazed together — the same basic process that you use in plumbing or refrigeration, where you permanently join pipes with a filler alloy and a propane torch. Unfortunately, almost every useful braze filler out there is chock full of silver, and silver just loves to transmute into cadmium. Cadmium is (A) extremely toxic, and (B) pretty dang brittle.
So basically, I’m sourcing weirder braze fillers that don’t have any silver, among other restrictions. They are more expensive and finicky, but at the end of the day this is more of a fun engineering challenge than an actual problem. I’m not worried about losing my state alchemist’s license or anything!










